In some materials a mitosis-like phase of chromosome contraction (spiralization) occurs between interphase and leptotene; leptotene follows despiralization of these contracted chromosomes. The degree of chromosome contraction can be extremely variable, within individuals and among different species or genera of plants and animals. This "preleptotene chromosome contraction" has been described and illustrated by the applicant in Lilium, and it was shown that degree of contraction may be related to sequence of development of meiocytes in individual anthers. Preliminary observations indicated that the degree of preleptotene chromosome contraction may differ in various cultivars of Lilium. The overall objectives of the present study are: Determination of the limits of variability, the effect of sequence of microsporocyte development, and the influence of different genetic backgrounds on degree of preleptotene chromosome contraction. The materials used are cultivars of Lilium longiflorum, 'Ace,' 'Croft', and 'Nellie White.'